This invention relates to production of false-twist textured yarn of polyester filaments, and is more particularly concerned with a process for producing a feed yarn for draw-texturing into yarn having distributed therethrough portions which dye to deeper shades than other portions of the yarn.
Conventional processes for producing textile yarns of polyester filaments have involved melt-spinning polyethylene terephthalate into yarn at take-off speeds of 500 to 1,500 meters per minute (500 to 1,640 yards/minute). The take-off speed refers to the speed of the solidified yarn at windup or at roll for forwarding the yarn to subsequent processing.
Conventional as-spun yarn is usually drawn at a draw ratio of about 3.5 to 4.5X (3.5 to 4.5 times greater length) to produce the fully-drawn, uniform yarn of commerce. Alternatively, the yarn can be incompletely drawn to provide a random distribution of thick and thin sections along the filaments, of which the incompletely drawn thick sections have a higher dye uptake (dye to deeper shades) to provide attractive dyed fabrics. Lewis U.S. Pat. No. 2,278,888 discloses in Example V that the thin sections can be formed at desired locations along the yarn by contacting these portions of the yarn with a heated surface during drawing. Bates U.S. Pat. No. 3,662,055 discloses a programmed heating of portions along the yarn with a flame as the yarn is drawn. A running yarn can be intermittently vibrated in and out of contact with the flame by means of an electromagnetic vibrator acting on guides through which the yarn is passing. The vibrator can be programmed electrically according to any desired periodical or random or psuedo-random program and the program will be reproduced along the yarn in a corresponding arrangement of thick and thin sections. Instead of vibrating the yarn, the flame can be deflected in and out of contact with the yarn by modulating the flame or by deflecting the flame with an impinging stream of gas which is modulated in a programmed manner.
Petrille U.S. Pat. No. 3,771,307 discloses a false-twist texturing process for texturing spin-oriented polyester yarn prepared by melt-spinning at take-off speeds of 3,000 to 4,000 yards per minute (2,744 to 3,660 meters/minute). The as-spun yarn is drawn at a draw ratio of 1.3 to 2.0 as it is false-twist textured. The above methods, of intermittently heating conventional yarn while incompletely drawing the yarn to form thick and thin sections along the yarn, will not accomplish the desired result when used to produce a feed yarn for false-twist texturing processes. The incompletely drawn thick sections will melt or stick together at the high heater temperature used to set crimp in the yarn, or will be fully drawn at the tensions used. Spin-oriented yarn can be incompletely drawn while intermittently heating it to form thick and thin sections along the yarn, but the incompletely drawn thick sections of this feed yarn will be fully drawn at the temperatures and tensions used in draw-texturing processes and the desired deeper-dyeing sections will not be obtained.